Background Art In the prior art, a heating apparatus, designed to perform its heating function by taking advantage of the phase change of the refrigerant to dissipate heat from hot refrigerant to a target room using the phase change of the refrigerant, has been proposed and widely used. In a heating operation, the heating apparatus repeatedly carries out a refrigerating cycle where refrigerant is sequentially subjected to a compression process, a condensation process, an expansion process, and an evaporation process prior to being returned to the compression process.

Such a heating apparatus comprises an indoor unit, an outdoor unit, a compressor, and an expansion unit. The indoor unit of the heating apparatus is installed within a room, while the outdoor unit is installed outside the room. The compressor adiabatically compresses low temperature, low pressure gas refrigerant from the outdoor unit to discharge high temperature, high pressure gas refrigerant.

The expansion unit adiabatically expands high temperature, high pressure liquid refrigerant from the indoor unit to discharge low temperature, low pressure liquid refrigerant. The indoor unit, outdoor unit, compressor, and expansion unit are connected together by a refrigerant pipeline to allow refrigerant to sequentially flow through them during an operation of the heating apparatus. A plurality of sensors are installed at predetermined positions of the apparatus to sense the temperature and pressure of the refrigerant. The operation of the heating apparatus is controlled by a controller, which controls power supply for the

electrically operable elements, such as the compressor, the sensors, etc., in addition to controlling the operation of the elements in response to signals output from the sensors.

The conventional heating apparatus is operated as follows when it is desired to heat a target room.

At the indoor unit, high temperature, high pressure gas refrigerant dissipates heat to air inside the target room, thus being condensed to become high temperature, high pressure liquid refrigerant prior to being discharged to the expansion unit. The expansion unit adiabatically expands the high temperature, high pressure liquid refrigerant from the indoor unit to discharge low temperature, low pressure liquid refrigerant to the outdoor unit. At the outdoor unit, the low temperature, low pressure liquid refrigerant from the expansion unit absorbs heat from atmospheric air, thus being evaporated to become low temperature, low pressure gas refrigerant prior to being discharged to the compressor. At the compressor, the low temperature, low pressure gas refrigerant from the outdoor unit is compressed to become high temperature, high pressure gas refrigerant prior to being discharged to the indoor unit. The heating apparatus thus finishes one operation cycle.

In such conventional heating apparatuses, it is typical to control the temperature of inlet refrigerant of the compressor such that the temperature is increased to slightly exceed the saturation point of the refrigerant, where the refrigerant includes both a gas phase portion and a liquid phase portion. When the temperature of the inlet refrigerant of the compressor is increased as described above, the inlet refrigerant is converted entirely to gas refrigerant. When refrigerant including a liquid phase portion flows into the compressor, the refrigerant may undesirably deteriorate the refrigerant compressing capability of the compressor, in addition to damaging or breaking the parts of the compressor.

When the temperature of inlet refrigerant of the compressor is increased excessively to exceed the saturation point of the refrigerant, the inlet refrigerant may thermally damage the parts of the compressor to cause a thermal deterioration of the parts and undesirably shorten the expected life span of the compressor, in

addition to remarkably reducing the compression efficiency of the compressor.

However, such conventional heating apparatuses do not include any means for appropriately controlling the conditions of inlet refrigerant of its compressor, and so the inlet refrigerant of the compressor undesirably has a temperature excessively exceeding the saturation point of the refrigerant, where the refrigerant includes both a gas phase portion and a liquid phase portion.

The compressor's inlet refrigerant having such an excessively increased temperature thermally damages the parts of the compressor to cause a thermal deterioration of the parts and undesirably shorten the expected life span of the compressor, and forces the owner of the heating apparatus to waste time and pay money for repairing the heating apparatus.

The inlet refrigerant having such an excessively increased temperature also undesirably causes the outlet refrigerant from the compressor to have excessively high temperature or excessively low pressure.

When the outlet refrigerant from the compressor has an excessively high temperature, it is necessary for the refrigerant to dissipate an excessively large quantity of heat to a room during a condensation process. When the outlet refrigerant from the compressor has an excessively low pressure, it is almost impossible to desirably condense the refrigerant during the condensation process since the temperature of the refrigerant is too low. Either of the two cases undesirably reduces the heating effect of the heating apparatus.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a heating apparatus, which is designed to prevent the temperature of the inlet refrigerant of its compressor from being increased excessively to exceed the saturation point of the refrigerant with both a gas phase portion and a liquid phase portion of the refrigerant, and which thus preferably reduces the compression load of the compressor.

Another object of the present invention is to provide a heating apparatus, which reduces the compression load of its compressor, thus being free from a reduction in its heating efficiency.

A further object of the present invention is to provide a heating apparatus, which reduces the compression load of its compressor, thus being free from a thermal deterioration of the compressor's parts or a reduction in the expected life span of the compressor.

In order to accomplish the above objects, the primary embodiment of the present invention provides a heating apparatus designed such that the refrigerant from the indoor unit passes through a heat exchanging and evaporating unit prior to flowing into the expansion unit, with the refrigerant from the heat exchanging and evaporating unit partially flowing into a sub-expansion unit to become low temperature, low pressure bypassed refrigerant, the bypassed refrigerant flowing from the sub-expansion unit passing through the heat exchanging and evaporating unit prior to flowing into the compressor.

The second embodiment of the present invention provides a heating apparatus designed such that the refrigerant from the indoor unit passes through a heat exchanging and evaporating unit prior to flowing into the expansion unit, with the refrigerant from the heat exchanging and evaporating unit partially flowing into a sub-expansion unit to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and the refrigerant flowing from the outdoor unit passing through the heat exchanging and evaporating unit prior to flowing into the compressor.

The third embodiment of the present invention provides a heating apparatus designed such that the refrigerant from the indoor unit passes through a heat exchanging and evaporating unit prior to flowing into the expansion unit, with the refrigerant from the heat exchanging and evaporating unit partially flowing into a sub-expansion unit to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and passing through the heat exchanging and evaporating unit and the refrigerant flowing from the outdoor unit and passing through the expansion unit commonly

flowing into the compressor.

The fourth embodiment of the present invention provides a heating apparatus designed such that the refrigerant from the indoor unit passes through a heat exchanging and evaporating unit prior to flowing into the expansion unit, with the refrigerant from the heat exchanging and evaporating unit partially flowing into a sub-expansion unit to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and the refrigerant flowing from the outdoor unit and passing through the expansion unit commonly passing through the heat exchanging and evaporating unit prior to flowing into the compressor.

Brief Description of the Drawings The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram of a heating apparatus with low compression load in accordance with the primary embodiment of the present invention; Fig. 2 is a sectional view of a heat exchanging and evaporating unit included in the heating apparatus of Fig. 1 ; Fig. 3 is a block diagram of a heating apparatus in accordance with a modification of the primary embodiment of this invention; Fig. 4 is a sectional view of a heat exchanging and evaporating unit included in the heating apparatus of Fig. 3; Fig. 5 is a block diagram of a heating apparatus with low compression load in accordance with the second embodiment of the present invention; Fig. 6 is a block diagram of a heating apparatus in accordance with a modification of the second embodiment of this invention; Fig. 7 is a block diagram of a heating apparatus with low compression load in accordance with the third embodiment of the present invention; Fig. 8 is a block diagram of a heating apparatus in accordance with a

modification of the third embodiment of this invention; Fig. 9 is a block diagram of a heating apparatus with low compression load in accordance with the fourth embodiment of the present invention; and Fig. 10 is a block diagram of a heating apparatus in accordance with a modification of the fourth embodiment of this invention.

Best Mode for Carrying Out the Invention Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.

Fig. 1 is a block diagram of a heating apparatus with low compression load in accordance with the primary embodiment of the present invention. As shown in the drawing, the heating apparatus 100 according to the primary embodiment comprises an expansion unit 120, an indoor unit 140, a compressor 150, and an outdoor unit 160. The outdoor unit 160 evaporates the refrigerant flowing from the expansion unit 120. The compressor 150 compresses the refrigerant flowing from the outdoor unit 160. The indoor unit 140 condenses the refrigerant flowing from the compressor 150.

A heat exchanging and evaporating unit 110 is mounted to the refrigerant pipeline between the indoor unit 140 and the expansion unit 120. This heat exchanging and evaporating unit 110 has a first refrigerant inlet port 111 and a first refrigerant outlet port 113, through which the evaporating unit 110 receives the refrigerant from the indoor unit 140 and discharges the refrigerant to the expansion unit 120. The refrigerant pipe 116 extending from the first refrigerant outlet port 113 of the evaporating unit 110 to the expansion unit 120 is divided into two pipes: a main pipe 117 and a bypass pipe 115. During an operation of the heating apparatus, the refrigerant from the evaporating unit 110 partially flows to the expansion unit 120 through the main pipe 117. For example, 50% of the refrigerant from the evaporating unit 110 flows to the expansion unit 120. The remaining part of the refrigerant from the evaporating unit 110 flows into a sub-

expansion unit 130 through the bypass pipe 115. The sub-expansion unit 130 discharges the refrigerant to the evaporating unit 110. In such a case, the evaporating unit 110 receives the refrigerant from the sub-expansion unit 130 through its second refrigerant inlet port 112, and discharges the refrigerant to the compressor 150 through its second refrigerant outlet port 114. Therefore, the compressor 150 receives refrigerant from both the outdoor unit 160 and the evaporating unit 110.

The construction of the sub-expansion unit 130 is similar to that of the main expansion unit 120, and so pressure of the refrigerant discharged from the sub-expansion unit 130 is equal or similar to that from the main expansion unit 120. In the evaporating unit 110, the low temperature, low pressure refrigerant flowing from the second refrigerant inlet port 112 absorbs heat from the high temperature, high pressure refrigerant flowing from the first refrigerant inlet port 111. Therefore, the evaporating unit 110 discharges high pressure refrigerant having a reduced temperature through the first refrigerant outlet port 113, and discharges low pressure refrigerant having an increased temperature through the second refrigerant outlet port 114.

In the present invention, the heat exchanging and evaporating unit 110 may have a variety of constructions. An example of the construction of the evaporating unit 110 is shown in Fig. 2. As shown in the drawing, the evaporating unit 110 comprises a hollow housing 1 1 Oa having a cavity 11 Ob, with the first refrigerant inlet port 111 and the first refrigerant outlet port 113 formed at both ends of the housing 110a. The first refrigerant inlet port 111 and the first refrigerant outlet port 113 are connected to the indoor unit 140 and the expansion unit 120 through two refrigerant pipes Illa and 116, respectively. The first refrigerant inlet port 111 and the first refrigerant outlet port 113 are connected to each other by a coil-shaped pipe 119 within the housing 110a. In addition, the second refrigerant inlet port 112 is formed on the housing 110a at a position around the first refrigerant outlet port 113, while the second refrigerant outlet port 114 is formed on the housing 110a at a position around the first refrigerant inlet port 11 l. The second refrigerant inlet port 112 and the second refrigerant outlet

port 114 are connected to the sub-expansion unit 130 and the compressor 150 through two refrigerant pipes 112a and 114a, respectively. Therefore, the refrigerant, flowing into the housing 11 osa of the evaporating unit 110 through the second refrigerant inlet port 112, comes into contact with the external surface of the coil-shaped pipe 119 to absorb heat from the refrigerant, flowing in the coil- shaped pipe 119, prior to being discharged from the housing 110a to the compressor 150 through the second refrigerant outlet port 114.

Fig. 3 is a block diagram of a heating apparatus in accordance with a modification of the primary embodiment of this invention. As shown in the drawing, the construction of the heating apparatus 100'according to the modification is similar to that of the heating apparatus 100 of the primary embodiment. However, the heat exchanging and evaporating unit 110'comprises two or more evaporating units 110A and 110B, which are arranged on the refrigerant pipeline of the apparatus 100'in a parallel arrangement or a series arrangement. In addition, the expansion unit 120'comprises two or more expansion units 120A and 120B, which are arranged on the refrigerant pipeline of the apparatus 100'in a parallel arrangement or a series arrangement. The compressor 150'comprises two-stage compressors 150A and 150B. The sub- expansion unit 130'comprises two or more sub-expansion units 130A and 130B, which are arranged on the refrigerant pipeline of the apparatus 100'in a parallel arrangement or a series arrangement.

The first evaporating unit 110A connected to the indoor unit 140'has a first refrigerant inlet port 111'and a second refrigerant outlet port 114', while the second evaporating unit HOB connected to the expansion unit 120'has a second refrigerant inlet port 112'and a first refrigerant outlet port 113'. The refrigerant from the first refrigerant outlet port 113'of the second evaporating unit 110B partially flows into the sub-expansion unit 130'through a bypass pipe 115'. The sub-expansion unit 130'discharges the refrigerant to the evaporating unit 110'.

In such a case, the evaporating unit 110'receives the refrigerant from the sub- expansion unit 130'through its second refrigerant inlet port 112', and discharges the refrigerant to the first compressor 150A through its second refrigerant outlet

port 114'. Therefore, the first compressor 150A receives refrigerant from both the outdoor unit 160'and the evaporating unit 110'. At the compressor 150', the refrigerant is sequentially processed by the first and second compressors 150A and 150B, and is discharged to the indoor unit 140'.

An example of the construction of the evaporating unit 110'is shown in Fig. 4. As shown in the drawing, the evaporating unit 110'comprises the first evaporating unit 110A having a hollow housing 11 OA', and the second evaporating unit HOB having a hollow housing HOB'. The two evaporating units 110A and HOB are connected to each other through a connection duct 11 OC. The first refrigerant inlet port 111'of the first evaporating unit 110A is connected to the indoor unit 140'through a refrigerant pipe 111 a', while the first refrigerant outlet port 113'of the second evaporating unit HOB is connected to the expansion unit 120'through a refrigerant pipe 116'. The housing 110A'of the first evaporating unit 11 OA having the first refrigerant inlet port 111'also has the second refrigerant outlet port 114', which is connected to the compressor 150'through a pipe 114a'.

The housing 1 1 OB'of the second evaporating unit HOB having the first refrigerant outlet port 113'also has the second refrigerant inlet port 112', which is connected to the sub-expansion unit 130'through a pipe 112a'. The first refrigerant inlet port 111'and the first refrigerant outlet port 113'are connected to each other by two coil-shaped pipes 119A and 119B and a connection pipe 118'. The two coil- shaped pipes 119A and 119B are set within the two housings 110A'and HOB' respectively, while the connection pipe 118'extends within the connection duct 11 OC and connects the two coil-shaped pipes 119A and 119B to each other.

The heating apparatus 100'according to the modification of the primary embodiment is improved in its heat exchanging capability, refrigerant expanding capability and refrigerant compressing capability since it has the multi-stage evaporating unit 110', multi-stage expansion unit 120', multi-stage sub-expansion unit 130'and multi-stage compressor 150', different from the heating apparatus 100 according to the primary embodiment. This modification is preferable since it is possible to improve the heating capability of the heating apparatus 100', in addition to reducing load applied to the elements of the heating apparatus 100'.

In the heating apparatus 100', it is preferable to mount a refrigerant dispenser 126 on the refrigerant pipe extending from the refrigerant outlet port of the sub-expansion unit 130'so as to feed the refrigerant from the sub-expansion unit 130'to both evaporating units 110A and 110B, or feed either of the two evaporating units 110A and HOB as desired. In such a case, the pipe extending from the refrigerant outlet port of the sub-expansion unit 130'is connected to the refrigerant inlet ports 112'and 112"of the two evaporating units HOB and 110A through two pipes 112a'and 112a"commonly extending from the refrigerant dispenser 126.

During an operation of the heating apparatus 100', the quantity of heat transferred between two types of refrigerants commonly flowing in the evaporating unit 110'varies in accordance with the operational mode of the refrigerant dispenser 126. This means that it is possible to control the operation of the heating apparatus 100'in a variety of operational modes.

Fig. 5 is a block diagram of a heating apparatus with low compression load in accordance with the second embodiment of the present invention. As shown in the drawing, the heating apparatus 200 according to the second embodiment comprises an expansion unit 220, an indoor unit 240, a compressor 250, and an outdoor unit 260. The outdoor unit 260 evaporates the refrigerant flowing from the expansion unit 220. The compressor 250 compresses the refrigerant flowing from the outdoor unit 260. The indoor unit 240 condenses the refrigerant flowing from the compressor 250.

A heat exchanging and evaporating unit 210 is mounted to the refrigerant pipeline between the indoor unit 240 and the expansion unit 220. This heat exchanging and evaporating unit 210 has a first refrigerant inlet port 211 and a first refrigerant outlet port 214, through which the evaporating unit 210 receives the refrigerant from the indoor unit 240 and discharges the refrigerant to the expansion unit 220. A bypass pipe 216 branches from a main pipe 217, which extends from the first refrigerant outlet port 214 of the evaporating unit 210 to the expansion unit 220. During an operation of the heating apparatus 200, the refrigerant from the evaporating unit 210 partially flows to the expansion unit 220 through the main

pipe 217. The remaining part of the refrigerant from the evaporating unit 210 flows into a sub-expansion unit 230 through the bypass pipe 216. The sub- expansion unit 230 discharges the refrigerant to the evaporating unit 210. In such a case, the evaporating unit 210 receives the refrigerant from the sub-expansion unit 230 through its second refrigerant inlet port 212. In addition, the evaporating unit 210 also receives the refrigerant from the outdoor unit 260 through its third refrigerant inlet port 213. Therefore, the refrigerant flowing into the evaporating unit 210 through the second refrigerant inlet port 212 is mixed with the refrigerant flowing into the evaporating unit 210 through the third refrigerant inlet port 213, thus forming mixed refrigerant. This mixed refrigerant absorbs heat from the refrigerant flowing into the evaporating unit 210 through the first refrigerant inlet port 211, and is discharged to the compressor 250 through a second refrigerant outlet port 215 of the evaporating unit 210.

The construction of the sub-expansion unit 230 is similar to that of the main expansion unit 220, and so pressure of the refrigerant discharged from the sub-expansion unit 230 is equal or similar to that from the main expansion unit 220. In the evaporating unit 210, the mixed refrigerant, formed by mixing the low temperature, low pressure refrigerant flowing from the second refrigerant inlet port 212 with the middle temperature, middle pressure refrigerant flowing from the third refrigerant inlet port 213, absorbs heat from the high temperature, high pressure refrigerant flowing from the first refrigerant inlet port 211. Therefore, the evaporating unit 210 discharges high pressure refrigerant having a reduced temperature through the first refrigerant outlet port 214, and discharges low pressure refrigerant having an increased temperature through the second refrigerant outlet port 215.

In the present invention, the heat exchanging and evaporating unit 210 may have a variety of constructions. The general construction of the evaporating unit 210 remains the same as that described for the evaporating unit 110 of Fig. 2 according to the primary embodiment, and further explanation is thus not deemed necessary. However, it should be understood that the evaporating unit 210 of this second embodiment must be designed such that the unit 210 mixes the refrigerant

from the second refrigerant inlet port 212 with the refrigerant from the third refrigerant inlet port 213 to form mixed refrigerant prior to discharging the mixed refrigerant through the second refrigerant outlet port 215.

Fig. 6 is a block diagram of a heating apparatus in accordance with a modification of the second embodiment of this invention. As shown in the drawing, the construction of the heating apparatus 200'according to the modification is similar to that of the heating apparatus 200 of the second embodiment. However, the heat exchanging and evaporating unit 210'comprises two or more evaporating units 210A and 210B, which are arranged on the refrigerant pipeline of the apparatus 200'in a parallel arrangement or a series arrangement. In addition, the expansion unit 220'comprises two or more expansion units 220A and 220B, which are arranged on the refrigerant pipeline of the apparatus 200'in a parallel arrangement or a series arrangement. The compressor 250'comprises two-stage compressors 250A and 250B. The sub- expansion unit 230'comprises two or more sub-expansion units 230A and 230B, which are arranged on the refrigerant pipeline of the apparatus 200'in a parallel arrangement or a series arrangement.

The first evaporating unit 210A connected to the indoor unit 240'has a first refrigerant inlet port 211'and a second refrigerant outlet port 215', while the second evaporating unit 210B connected to the expansion unit 220'has a second refrigerant inlet port 212', a third refrigerant inlet port 213'and a first refrigerant outlet port 214'. The refrigerant from the first refrigerant outlet port 214'of the second evaporating unit 210B partially flows into the sub-expansion unit 230' through a bypass pipe 216'. The sub-expansion unit 230'discharges the refrigerant to the evaporating unit 210'. In such a case, the evaporating unit 210' receives the refrigerant from the sub-expansion unit 230'through its second refrigerant inlet port 212'. In addition, the refrigerant from the outdoor unit 260' entirely flows into the evaporating unit 210'through the third refrigerant inlet port 213'. Within the evaporating unit 210', the refrigerant from the outdoor unit 260' is mixed with the refrigerant from the sub-expansion unit 230'to form mixed refrigerant. The mixed refrigerant is, thereafter, discharged from the evaporating

unit 210'to the compressor 250'through the second refrigerant outlet port 215'.

Therefore, the first compressor 250A receives refrigerant from the evaporating unit 210'. At the compressor 250', the refrigerant is sequentially processed by the first and second compressors 250A and 250B, and is discharged to the indoor unit 240'.

The general construction of the evaporating unit 210'remains the same as that described for the evaporating unit 110'of Fig. 4 according to the primary embodiment, and further explanation is thus not deemed necessary. However, it should be understood that the evaporating unit 210'must be designed such that the unit 210'mixes the refrigerant from the second refrigerant inlet port 212'with the refrigerant from the third refrigerant inlet port 213'to form mixed refrigerant, which absorbs heat from the refrigerant from the indoor unit 240'prior to being discharged to the compressor 250'through the second refrigerant outlet port 215'.

The heating apparatus 200'according to the modification of the second embodiment is improved in its heat exchanging capability, refrigerant expanding capability and refrigerant compressing capability since it has the multi-stage evaporating unit 210', multi-stage expansion unit 220', multi-stage sub-expansion unit 230'and multi-stage compressor 250', different from the heating apparatus 200 according to the second embodiment. This modification is preferable since it is possible to improve the heating capability of the heating apparatus 200', in addition to reducing load applied to the elements of the heating apparatus 200'.

In the heating apparatus 200', it is preferable to mount a refrigerant dispenser 226 on the refrigerant pipe extending from the refrigerant outlet port of the sub-expansion unit 230'so as to feed the refrigerant from the sub-expansion unit 230'to both evaporating units 210A and 210B, or feed either of the two evaporating units 210A and-210B as desired. In such a case, the pipe extending from the refrigerant outlet port of the sub-expansion unit 230'is connected to the refrigerant inlet ports 212'and 212"of the two evaporating units 210B and 210A through two pipes 212a'and 212a"commonly extending from the refrigerant dispenser 226.

During an operation of the heating apparatus 200', the quantity of heat

transferred between refrigerants commonly flowing in the evaporating unit 210' varies in accordance with the operational mode of the refrigerant dispenser 226.

This means that it is possible to control the operation of the heating apparatus 200' in a variety of operational modes.

Fig. 7 is a block diagram of a heating apparatus with low compression load in accordance with the third embodiment of the present invention. As shown in the drawing, the heating apparatus 300 according to the third embodiment comprises an expansion unit 320, an indoor unit 340, a compressor 350, and an outdoor unit 360. The outdoor unit 360 evaporates the refrigerant flowing from the expansion unit 320. The compressor 350 compresses the refrigerant flowing from the outdoor unit 360. The indoor unit 340 condenses the refrigerant flowing from the compressor 350.

A heat exchanging and evaporating unit 310 is mounted to the refrigerant pipeline between the indoor unit 340 and the expansion unit 320. This heat exchanging and evaporating unit 310 has a first refrigerant inlet port 311 and a first refrigerant outlet port 313, through which the evaporating unit 310 receives the refrigerant from the indoor unit 340 and discharges the refrigerant to the expansion unit 320. The refrigerant pipe 316 extending from the first refrigerant outlet port 313 of the evaporating unit 310 to the expansion unit 320 is divided into two pipes: a main pipe 317 and a bypass pipe 315. During an operation of the heating apparatus 300, the refrigerant from the evaporating unit 310 partially flows to the expansion unit 320 through the main pipe 317. The remaining part of the refrigerant from the evaporating unit 310 flows into a sub-expansion unit 330 through the bypass pipe 315. The sub-expansion unit 330 discharges the refrigerant to the evaporating unit 310. In such a case, the evaporating unit 310 receives the refrigerant from the sub-expansion unit 330 through its second refrigerant inlet port 312, and discharges the refrigerant through its second refrigerant outlet port 314.

The construction of the sub-expansion unit 330 is similar to that of the main expansion unit 320, and so pressure of the refrigerant discharged from the sub-expansion unit 330 is equal or similar to that from the main expansion unit

320. In the evaporating unit 310, the low temperature, low pressure refrigerant flowing from the second refrigerant inlet port 312 absorbs heat from the high temperature, high pressure refrigerant flowing from the first refrigerant inlet port 311. Therefore, the evaporating unit 310 discharges high pressure refrigerant having a reduced temperature through the first refrigerant outlet port 313, and discharges low pressure refrigerant having an increased temperature through the second refrigerant outlet port 314.

In the present invention, the heat exchanging and evaporating unit 310 may have a variety of constructions. The general construction of the evaporating unit 310 remains the same as that described for the evaporating unit 110 of Fig. 2 according to the primary embodiment, and further explanation is thus not deemed necessary.

In the heating apparatus 300 according to the third embodiment, the expansion unit 320 receives refrigerant from the main pipe 317, and expands the refrigerant to form low temperature, low pressure refrigerant prior to discharging the refrigerant to the outdoor unit 360. The expansion unit 320 has a refrigerant inlet port 321 and a refrigerant outlet port 322, and receives the entire refrigerant from the outdoor unit 360 through the refrigerant inlet port 321, and discharges the refrigerant to the compressor 350 through the refrigerant outlet port 322.

Therefore, the expansion unit 320 performs a heat exchanging process. Since the expansion unit 320 has the same construction as that of a conventional expansion unit, the detailed construction of the expansion unit 320 is not shown in the accompanying drawings. The expansion unit 320 includes an expansion valve (not shown) used for expanding the refrigerant flowing from the main pipe 317 to the outdoor unit 360. The expansion valve is encased by a housing (not shown), with the refrigerant inlet and outlet ports 321 and 322 formed in the housing.

Therefore, the refrigerant flowing into the expansion unit 320 through the refrigerant inlet port 321 comes into contact with the external surface of the expansion valve, and so heat is transferred between the refrigerant flowing inside the expansion valve and the refrigerant flowing outside the expansion valve to accomplish a desired heat exchanging process. After the heat exchanging

process, the refrigerant flowing from the refrigerant inlet port 321 is discharged from the expansion unit 320 to the compressor 350 through the refrigerant outlet port 322.

In such a case, the refrigerant flowing from the refrigerant outlet port 322 of the expansion unit 320 is mixed with the refrigerant flowing from the second refrigerant outlet port 314 of the evaporating unit 310 to form mixed refrigerant.

This mixed refrigerant flows into the compressor 350.

Fig. 8 is a block diagram of a heating apparatus in accordance with a modification of the third embodiment of this invention. As shown in the drawing, the construction of the heating apparatus 300'according to the modification is similar to that of the heating apparatus 300 of the third embodiment. However, the heat exchanging and evaporating unit 310'comprises two or more evaporating units 310A and 310B, which are arranged on the refrigerant pipeline of the apparatus 300'in a parallel arrangement or a series arrangement. In addition, the expansion unit 320'comprises two or more expansion units 320A and 320B, which are arranged on the refrigerant pipeline of the apparatus 300'in a parallel arrangement or a series arrangement. The compressor 350'comprises two-stage compressors 350A and 350B. The sub-expansion unit 330'comprises two or more sub-expansion units 330A and 330B, which are arranged on the refrigerant pipeline of the apparatus 300'in a parallel arrangement or a series arrangement.

The first evaporating unit 310A connected to the indoor unit 340'has a first refrigerant inlet port 311'and a second refrigerant outlet port 314', while the second evaporating unit 310B connected to the expansion unit 320'has a second refrigerant inlet port 312'and a first refrigerant outlet port 313'. The refrigerant from the first refrigerant outlet port 313'of the second evaporating unit 310B partially flows into the sub-expansion unit 330'through a bypass pipe 315'. The sub-expansion unit 330'discharges the refrigerant to the evaporating unit 310'.

In such a case, the evaporating unit 310'receives the refrigerant from the sub- expansion unit 330'through its second refrigerant inlet port 312', and discharges refrigerant through the second refrigerant outlet port 314'. In addition, the refrigerant from the expansion unit 320'and the refrigerant from the second

refrigerant outlet port 314'of the evaporating unit 310'flow into the compressor 350'. At the compressor 350', the refrigerant is sequentially processed by the first and second compressors 350A and 350B, and is discharged to the indoor unit 340'.

The general construction of the evaporating unit 310'remains the same as that described for the evaporating unit 110'of Fig. 4 according to the primary embodiment, and further explanation is thus not deemed necessary.

The heating apparatus 300'according to the modification of the third embodiment is improved in its heat exchanging capability, refrigerant expanding capability and refrigerant compressing capability since it has the multi-stage evaporating unit 310', multi-stage expansion unit 320', multi-stage sub-expansion unit 330'and multi-stage compressor 350', different from the heating apparatus 300 according to the third embodiment. This modification is preferable since it is possible to improve the heating capability of the heating apparatus 300', in addition to reducing load applied to the elements of the heating apparatus 300'.

In the heating apparatus 300', it is preferable to mount a refrigerant dispenser 326 on the refrigerant pipe extending from the refrigerant outlet port of the sub-expansion unit 330'so as to feed the refrigerant from the sub-expansion unit 330'to both evaporating units 310A and 310B, or feed either of the two evaporating units 310A and 310B as desired. In such a case, the pipe extending from the refrigerant outlet port of the sub-expansion unit 330'is connected to the refrigerant inlet ports 312'and 312"of the two evaporating units 310B and 310A through two pipes 312a'and 312a"commonly extending from the refrigerant dispenser 326.

During an operation of the heating apparatus 300', the quantity of heat transferred between refrigerants commonly flowing in the evaporating unit 310' varies in accordance with the operational mode of the refrigerant dispenser 326.

This means that it is possible to control the operation of the heating apparatus 300' in a variety of operational modes.

Fig. 9 is a block diagram of a heating apparatus with low compression load in accordance with the fourth embodiment of the present invention. As

shown in the drawing, the heating apparatus 400 according to the fourth embodiment comprises an expansion unit 420, an indoor unit 440, a compressor 450, and an outdoor unit 460. The outdoor unit 460 evaporates the refrigerant flowing from the expansion unit 420. The compressor 450 compresses the refrigerant flowing from the outdoor unit 460. The indoor unit 440 condenses the refrigerant flowing from the compressor 450.

A heat exchanging and evaporating unit 410 is mounted to the refrigerant pipeline between the indoor unit 440 and the expansion unit 420. This heat exchanging and evaporating unit 410 has a first refrigerant inlet port 411 and a first refrigerant outlet port 414, through which the evaporating unit 410 receives the refrigerant from the indoor unit 440 and discharges the refrigerant to the expansion unit 420. The refrigerant pipe extending from the first refrigerant outlet port 414 of the evaporating unit 410 to the expansion unit 420 is divided into two pipes: a main pipe 417 and a bypass pipe 416. During an operation of the heating apparatus 400, the refrigerant from the evaporating unit 410 partially flows to the expansion unit 420 through the main pipe 417. The remaining part of the refrigerant from the evaporating unit 410 flows into a sub-expansion unit 430 through the bypass pipe 416. The sub-expansion unit 430 discharges the refrigerant to the evaporating unit 410. In such a case, the evaporating unit 410 receives the refrigerant from the sub-expansion unit 430 through its second refrigerant inlet port 412.

The construction of the sub-expansion unit 430 is similar to that of the main expansion unit 420, and so pressure of the refrigerant discharged from the sub-expansion unit 430 is equal or similar to that from the main expansion unit 420. In the evaporating unit 410, the mixed refrigerant, formed by mixing the low temperature, low pressure refrigerant flowing from the second refrigerant inlet port 412 with the middle temperature, middle pressure refrigerant flowing from the third refrigerant inlet port 413, absorbs heat from the high temperature, high pressure refrigerant flowing from the first refrigerant inlet port 411. Therefore, the evaporating unit 410 discharges high pressure refrigerant having a reduced temperature through the first refrigerant outlet port 414, and discharges low

pressure refrigerant having an increased temperature through the second refrigerant outlet port 415.

In the present invention, the heat exchanging and evaporating unit 410 may have a variety of constructions. The general construction of the evaporating unit 410 remains the same as that described for the evaporating unit 110 of Fig. 2 according to the primary embodiment, and further explanation is thus not deemed necessary. However, it should be understood that the evaporating unit 410 of this fourth embodiment must be designed such that the unit 410 mixes the refrigerant from the second refrigerant inlet port 412 with the refrigerant from the third refrigerant inlet port 413 to form mixed refrigerant prior to discharging the mixed refrigerant through the second refrigerant outlet port 415.

In the heating apparatus 400 according to the fourth embodiment, the expansion unit 420 receives refrigerant from the main pipe 417, and expands the refrigerant to form low temperature, low pressure refrigerant prior to discharging the refrigerant to the outdoor unit 460. The expansion unit 420 has a refrigerant inlet port 421 and a refrigerant outlet port 422, and receives the entire refrigerant from the outdoor unit 460 through the refrigerant inlet port 421, and discharges the refrigerant to the evaporating unit 410 through the refrigerant outlet port 422.

Therefore, the expansion unit 420 performs a heat exchanging process. Since the expansion unit 420 has the same construction as that of a conventional expansion unit, the detailed construction of the expansion unit 420 is not shown in the accompanying drawings and further explanation is not deemed necessary.

In such a case, the refrigerant flowing from the sub-expansion unit 430 into the evaporating unit 410 through the second refrigerant inlet port 412 is mixed with the refrigerant flowing from the refrigerant outlet port 422 of the expansion unit 420 into the evaporating unit 410 through the third refrigerant inlet port 413 to form mixed refrigerant. This mixed refrigerant absorbs heat from the refrigerant flowing into the evaporating unit 410 through the first refrigerant inlet port 411, and is discharged to the compressor 450 through the second refrigerant outlet port 415.

Fig. 10 is a block diagram of a heating apparatus in accordance with a

modification of the fourth embodiment of this invention. As shown in the drawing, the construction of the heating apparatus 400'according to the modification is similar to that of the heating apparatus 400 of the fourth embodiment. However, the heat exchanging and evaporating unit 410'comprises two or more evaporating units 410A and 41 OB, which are arranged on the refrigerant pipeline of the apparatus 400'in a parallel arrangement or a series arrangement. In addition, the expansion unit 420'comprises two or more expansion units 420A and 420B, which are arranged on the refrigerant pipeline of the apparatus 400'in a parallel arrangement or a series arrangement. The compressor 450'comprises two-stage compressors 450A and 450B. The sub- expansion unit 430'comprises two or more sub-expansion units 430A and 430B, which are arranged on the refrigerant pipeline of the apparatus 400'in a parallel arrangement or a series arrangement.

The first evaporating unit 410A connected to the indoor unit 440'has a first refrigerant inlet port 411'and a second refrigerant outlet port 415', while the second evaporating unit 410B connected to the expansion unit 420'has a second refrigerant inlet port 412', a third refrigerant inlet port 413'and a first refrigerant outlet port 414'. The refrigerant from the first refrigerant outlet port 414'of the second evaporating unit 410B partially flows into the sub-expansion unit 430' through a bypass pipe 416'. The entire refrigerant from the outdoor unit 460' passes through the expansion unit 420', and flows into the evaporating unit 410' through the third refrigerant inlet port 413', and is mixed with the refrigerant flowing from the sub-expansion unit 430'into the evaporating unit 410'through the second refrigerant inlet port 412', thus forming mixed refrigerant. This mixed refrigerant is discharged to the compressor 450'through the second refrigerant outlet port 415'. At the compressor 450', the refrigerant from the second refrigerant outlet port 415'of the evaporating unit 410'is sequentially processed by the first and second compressors 450A and 450B, and is discharged to the indoor unit 440'.

The general construction of the evaporating unit 410'remains the same as that described for the evaporating unit 110'of Fig. 4 according to the primary

embodiment, and further explanation is thus not deemed necessary. However, it should be understood that the evaporating unit 410'must be designed such that the unit 410'mixes the refrigerant from the second refrigerant inlet port 412'with the refrigerant from the third refrigerant inlet port 413'to form mixed refrigerant prior to discharging the mixed refrigerant to the compressor 450'through the second refrigerant outlet port 415'.

The heating apparatus 400'according to the modification of the fourth embodiment is improved in its heat exchanging capability, refrigerant expanding capability and refrigerant compressing capability since it has the multi-stage evaporating unit 410', multi-stage expansion unit 420', multi-stage sub-expansion unit 430'and multi-stage compressor 450', different from the heating apparatus 400 according to the fourth embodiment. This modification is preferable since it is possible to improve the heating capability of the heating apparatus 400', in addition to reducing load applied to the elements of the heating apparatus 400'.

In the heating apparatus 400', it is preferable to mount a refrigerant dispenser 426 on the refrigerant pipe extending from the refrigerant outlet port of the sub-expansion unit 430'so as to feed the refrigerant from the sub-expansion unit 430'to both evaporating units 410A and 410B, or feed either of the two evaporating units 410A and 410B as desired. In such a case, the pipe extending from the refrigerant outlet port of the sub-expansion unit 430'is connected to the refrigerant inlet ports 412'and 412"of the two evaporating units 410B and 410A through two pipes 412a'and 412a"commonly extending from the refrigerant dispenser 426.

During an operation of the heating apparatus 400', the quantity of heat transferred between refrigerants commonly flowing in the evaporating unit 410' varies in accordance with the operational mode of the refrigerant dispenser 426.

This means that it is possible to control the operation of the heating apparatus 400' in a variety of operational modes.

In the primary to fourth embodiments of this invention, the heating apparatus with low compression load has one indoor unit 140,240,340 or 440.

However, the heating apparatus of this invention may have a plurality of indoor

units, which are arranged on the refrigerant pipeline of the apparatus in a parallel arrangement or a series arrangement, without affecting the functioning of this invention. In such a case, it is possible to control the heating apparatus to feed the refrigerant to all the indoor units or feed the refrigerant selected indoor units as desired.

The operational effect of the heating apparatus 100 according to the primary embodiment will be described herein below with reference to Fig. 1.

During a heating operation of the apparatus 100, the refrigerant flowing from the indoor unit 140 is reduced in its temperature from 25°C to 5°C while passing through the evaporating unit 110, and flows into the expansion unit 120.

The expansion unit 120 discharges the refrigerant to the outdoor unit 160 after making low temperature, low pressure refrigerant having a temperature of-15°C.

The refrigerant is increased in its temperature to 10°C while passing through the outdoor unit 160. The refrigerant having a temperature of 5°C flowing from the evaporating unit 110 partially flows into the sub-expansion unit 130 through the bypass pipe 115, and flows into the evaporating unit 110 after becoming low temperature, low pressure refrigerant having a temperature of-15°C. The bypassed refrigerant having a temperature of-15°C is increased in its temperature to 0°C while passing through the evaporating unit 110. Therefore, at the compressor 150, the refrigerant having a temperature of 0°C flowing from the second refrigerant outlet port 114 of the evaporating unit 110 is mixed with the refrigerant having a temperature of 10°C flowing from the outdoor unit 160 to form mixed refrigerant having a temperature of 0°C ~ 10°C prior to flowing into the compressor 150. The compressor 150 compresses the refrigerant having a temperature lower than that of a conventional heating apparatus, and so the compressor 150 is free from thermal deterioration of its elements. The compressor 150 is thus improved in its compression efficiency, and is effectively used for a desired lengthy period of time.

The operational effect of the heating apparatus 200 according to the second embodiment will be described herein below with reference to Fig. 5.

During a heating operation of the apparatus 200, the refrigerant flowing

from the indoor unit 240 is reduced in its temperature from 25°C to 5°C while passing through the evaporating unit 210, and flows into the expansion unit 220.

The expansion unit 220 discharges the refrigerant to the outdoor unit 260 after making low temperature, low pressure refrigerant having a temperature of-15°C.

The refrigerant is increased in its temperature to 10°C while passing through the outdoor unit 260. The refrigerant having a temperature of 5°C flowing from the evaporating unit 210 partially flows into the sub-expansion unit 230 through the bypass pipe 216, and flows into the evaporating unit 210 after becoming low temperature, low pressure refrigerant having a temperature of-15°C. At the evaporating unit 210, the refrigerant of 10°C from the outdoor unit 260 is mixed with the refrigerant of-15°C from the sub-expansion unit 230 to form mixed refrigerant. This mixed refrigerant has a predetermined temperature of, for example, 5°C, and is discharged from the evaporating unit 210 to the compressor 250. The compressor 250 compresses the refrigerant having a temperature lower than that of a conventional heating apparatus, and so the compressor 250 is free from thermal deterioration of its elements. The compressor 250 is thus improved in its compression efficiency, and is effectively used for a desired lengthy period of time.

The operational effect of the heating apparatus 300 according to the third embodiment will be described herein below with reference to Fig. 7.

During a heating operation of the apparatus 300, the refrigerant flowing from the indoor unit 340 is reduced in its temperature from 25°C to 5°C while passing through the evaporating unit 310, and flows into the expansion unit 320.

The expansion unit 320 discharges the refrigerant to the outdoor unit 360 after making low temperature, low pressure refrigerant having a temperature of-15°C.

The refrigerant is increased in its temperature to 10°C while passing through the outdoor unit 360. The refrigerant having a temperature of 5°C flowing from the evaporating unit 310 partially flows into the sub-expansion unit 330 through the bypass pipe 315, and flows into the evaporating unit 310 after becoming low temperature, low pressure refrigerant having a temperature of-15°C. At the evaporating unit 310, the refrigerant of-15°C from the sub-expansion unit 330 is

increased in its temperature to 0°C. In addition, the refrigerant of 10°C from the outdoor unit 360 is increased in its temperature to 15°C while passing through the expansion unit 320. The refrigerant of 0°C from the second refrigerant outlet port 314 of the evaporating unit 310 is mixed with the refrigerant of 15°C from the refrigerant outlet port 322 of the expansion unit 320, thus forming mixed refrigerant of about 5°C. This mixed refrigerant of about 5°C flows into the compressor 350. The compressor 350 compresses the refrigerant having a temperature lower than that of a conventional heating apparatus, and so the compressor 350 is free from thermal deterioration of its elements. The compressor 350 is thus improved in its compression efficiency, and is effectively used for a desired lengthy period of time.

The operational effect of the heating apparatus 400 according to the fourth embodiment will be described herein below with reference to Fig. 9.

During a heating operation of the apparatus 400, the refrigerant flowing from the indoor unit 440 is reduced in its temperature from 25°C to 5°C while passing through the evaporating unit 410, and flows into the expansion unit 420.

The expansion unit 420 discharges the refrigerant to the outdoor unit 460 after making low temperature, low pressure refrigerant having a temperature of-15°C.

The refrigerant is increased in its temperature to 10°C while passing through the outdoor unit 460. The refrigerant having a temperature of 5°C flowing from the evaporating unit 410 partially flows into the sub-expansion unit 430 through the bypass pipe 416, and flows into the evaporating unit 410 after becoming low temperature, low pressure refrigerant having a temperature of-15°C. In addition, the refrigerant of 10°C from the outdoor unit 460 is increased in its temperature to 15°C while passing through the expansion unit 420. At the evaporating unit 410, the refrigerant of 15°C flowing from the expansion unit 420 is mixed with the refrigerant of-15°C flowing from the sub-expansion unit 430 to form mixed refrigerant of 7°C ~ 10°C prior to flowing into the compressor 450. The compressor 450 thus compresses the refrigerant having a temperature lower than that of a conventional heating apparatus, and so the compressor 450 is free from thermal deterioration of its elements. The compressor 450 is thus improved in its

compression efficiency, and is effectively used for a desired lengthy period of time.

Industrial Applicability As described above, the present invention provides a heating apparatus with low compression load. This heating apparatus is designed to prevent the temperature of the inlet refrigerant of its compressor from being increased excessively to exceed the saturation point of the refrigerant with both a gas phase portion and a liquid phase portion of the refrigerant. This heating apparatus thus preferably reduces the compression load of the compressor.

The compressor of this heating apparatus is effectively usable for a desired lengthy period of time without being thermally damaged or broken, and so it allows a user to conveniently use the heating apparatus without consuming excessive time or labor for repairing the compressor.

The compressor of this heating apparatus also optimally compresses the refrigerant during an operation of the heating apparatus, thus being free from a reduction in its heating efficiency.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.